To date, no consensus exists regarding the optimal bowel preparation regimen to use in patients with inadequate cleansing due to the absence of clinical trials. Given 4% to 17% of colonoscopies have inadequate bowel preparation, there is a significant public health need to address this issue.(5-12, 21-23) A highly efficacious yet tolerable bowel preparation regimen is needed for these patients to ensure adequate cleansing for their next procedure. The objective of this multi-centre randomized clinical trial will be to compare the efficacy of two regimens in achieving adequate bowel preparation after failing to cleanse at the index colonoscopy.